Fun first competition day with the AVO Turbo ND...it took the class by storm with two drivers (Sean and I) trading best times through the day. More download later, four hours of sleep and exhausted, will post the pics for now.

More on Autocross yesterday. Turbos and Autocross have always been an interesting mix, fun and challenging. With a supercharged autocross Miata like our 2007 I like to throttle steer through the course, around cones, precision use of every inch of the course is possible and rotation around features with all the extra power is an easy flick of the throttle. It is very different with the turbo.... dial up the power and then focus more on just roughly hitting my apex marks and otherwise keeping it somewhere between each side of the course. Placing it inches to the cones while trying to summon full TURBO power carries far more risks of stepping rear out and slapping that cone beside you. And so it was yesterday that Sean and I both did our best times in morning practice, in afternoon competition we both did our best times in our first 'warm up' run, and we both seriously slapped some cones during our subsequent runs. Great fun, perhaps even more fun to race than the supercharger, but also a lot more like a shotgun than a sniper riffle. With the supercharger in the car for the last event my challenge was just figuring best use of the power curve, control and placement of the car within the confines of the cones was not a challenge. But hey, at the end of the day our newly TURBO ND was fastest Miata by several seconds, beat all the BMWs too at this BMW CLUB Autocross event.

Now time to applaud the San Diego BMW CLUB. If within reach of San Diego, my TOP pick for Autocross big fun is the BMW Club. Their course designs are a mix of traditional autocross and full on race track. Yesterday included a double U turn that was so tight you had to get down to almost walking pace, but you were then rewarded with expanding radius full acceleration through two gears long downhill sweeper that sent our Turbo high into third gear and the tires just trying to hold on as the speed grew....onto the next rise and slam the breaks and catch the twitching car as you enter a Slalom. Will post video soon. So much Fun, such a great course, kudos to all involved!

As for COOL BOOST, happy to report that with two drivers flogging the car back to back our radiator temps were stable even as we regularly set and reset top time. Oil was still warmer than I want, broke 230 F despite massive oil cooler. We had challenges with cooland and oil temps at Laguna and that led to cutting the grille, though we have upped our oil cooling game per the prior posts after Laguna, we have now added an oil heating boost mechanism...the turbo itself...that makes our oil cooling challenge even higher than before. As time permits will make some more additional refinements to our cooling scheme.

At the last event I got behind the wheel of our Project Race ND it had our Edelbrock Supercharger installed. Hopping in the driver's seat this time the AVO turbo kit would be force feeding the engine.

Right off the line I noticed a bigger surge in power once you hit ~3000RPM and the pull to redline was stronger than before. Very little lag was present but if you were off the power band you always had to anticipate the onset of power during the lower speed corners. On a big track this would be less of an issue and you would be in the sweet spot of the power band. However, like Brian said, no matter what you do the turbo will always be a bit more unpredictable than a supercharger and it makes hunting the apex more risky.

I knew the turbo would provide excellent sound suppression but I was still surprised just how quiet our RoadsterSport Race muffler with Max mid-pipe was. I am a big fan of quiet exhaust systems so this was music to my ears and kept my fatigue levels lower at the end of the day. The exhaust still had plenty of character snapping and popping at redline when rowing through the gears. The turbo on the other hand was very quiet and you might not realize it was turbocharged unless you were told.

The additional aero and tires also made for a FUN day at the autocross trading top time of the day with Brian until I hit a cone! Now the big question...which did I like better? At the end of the day I think it all depends on the application. For a street only car the Supercharger is the answer for me. For an all our track weapon give me the turbo and all the boost.

The GTC-300 is what's referred to as a "3D wing" because the shape of the wing changes across the width of it. This design favors being placed at the rear of a typical sedan shaped car; the center section of the wing is tilted less where the air is coming from over the top of the car at a downward angle, and the outer sections of the wing are tilted more where the air is coming around the side of the car at a more horizontal direction.

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Data below from APR. AOA refers to Angle of Attack (the angle of the wing). The below CFD tests were done in a "free stream" which means that the airflow was linear across the whole width of the wing. This means these numbers aren't entirely representative of the downforce/drag values you will get in the real world with this wing mounted behind the roofline of a car, but the data still helps to give an idea of the forces that the wing can generate. At an educated guess, I would expect that the values from the test below would all be slightly higher (more downforce) in the real world because the effective angle of the center section of the wing as it relates to the direction of airflow coming down over the roof of the car is greater than is shown in a free-stream test.

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Note that the forces are presented in Newtons. 1 Newton = 0.225 pound-force. So, with the wing set at the most conservative 0° angle, at just 80mph we already have 150 lbs of downforce. At a more aggressive angle of 10° at 120mph we have 450 lbs of downforce. Keep in mind these are free-stream numbers, so it's very likely we are seeing more downforce than this in the real world on the back of a car.

Working on the turbo. Figuring out gauge setup for our three AEM gauges, AFR, Boost Controller, Oil Temp. Testing Map with higher boost levels using the boost controller. Back to the dyno soon. Progress is being made, it spun the tires in 2nd gear yesterday during data collection, Rival 245/40 laying long black lines from about 25mph is fun!

Morning of Dyno Fun to figure out the 'happy' settings for the AEM boost control with AVO Turbo. Almost the first ND over 300 Ft/LBs....best run at 298 Ft/lbs. Torque is still a new record if memory serves me, our friends at TurboSource with big EFR turbo make another 30 peak hp (though comparison between different brands of dyno makes that conclusion a little fuzzy at best). Spread of results because we slowly raised the boost level in small increments to watch the results climb. If you are looking for the AVO Turbo Kit curves shown in the DSport magazine review of this kit, or what FM gets with BBR turbo, you can find it here at the lowest boost settings (low pinkish HP & TQ lines). But more interesting is what happens as we raise the boost with AEM boost controller, notice that peak HP doesn't change much, a function of the fast spooling small turbo and very tight skyactiv head flow at the upper end, but changing boost has a big impact on torque out of the hole.

Final settings best and lowest result at about 11.5 psi, letting it cool a bit so oil drops under 200F got the best result, the lower run is with oil at 210 F. That cooler run is 293 ft/lbs Torque, 218 HP. We are using prototype ACT upgraded clutch to hold this much torque. This is stock head, 100 octane. At some point will go back to our high flow head because we know from experience with the supercharger that the higher flowing head will bump the upper end and shift torque curve to the right, but would like to get E85 results with stock head first.

Hmm...where I have seen torque curves that look like this? The answer is some turbo diesels and Mazda's dyno graphs of next gen Skyactiv X. Current Skyactiv is essentially an application of mild diesel tech to a high compression gas motor. The next gen Skyactiv X is even more like a turbo diesel, with compression ignition much of the running time and a small supercharger. Here is Mazda's 91 RON dyno of next gen supercharged Skyactiv X torque, notice torque curve amazingly similar in shape to what we are getting with the AVO Turbo at higher boost settings, complete with early rpm torque peak that drops off as rpms climb, etc. Result is big fun pulling away from stop lights and for Autocross starts!

Another autocross testing day. BMW Club today, long course, easily 1.5 times length of our usual SCCA course. Combine extra long course and lots of torque and result was both Sean and I were melting the tires off the car before we could finish a run, the 225mm wide Hoosier tires just not near enough now that we have so much torque. So, tonight working on more roll and pull to get 245/40 Hoosiers under the car. Got em fit in the back with good roll and pull, front is going to take more work. For the many running STR with 245/40 Rivals the 245/40 Hoosier might sound like no big deal except the Hoosier is quite a bit wider in reality than the 200 TW STR tires, may need offset bushings in the front along with more roll/pull to get them installed right. Likely this car goes flares soon.

Brian wrote:Working on the turbo. Figuring out gauge setup for our three AEM gauges, AFR, Boost Controller, Oil Temp. Testing Map with higher boost levels using the boost controller. Back to the dyno soon. Progress is being made, it spun the tires in 2nd gear yesterday during data collection, Rival 245/40 laying long black lines from about 25mph is fun!

One thing I really like about having the AEM Boost controller in the driver's space is that I can now change boost settings on the fly. I can turn it 'off' and we have stock boost. I can turn it on and have "a" level boost or "b" level boost. We have the "b" as the higher setting at 11.5 PSI. As we continue to test oil cooler position in the car this adjustable on the fly boost level is very convenient, and I can imagine track days where we crank it in the cooler morning runs and dial it back as the day heats up, etc.

As we have raised boost our need for more and more oil cooling has become more apparent. The Mishimoto oil cooler worked quite well for normal aspiration but proved not enough once we were racing boosted with supercharger and now the turbo. Thus, we have been working on even more OIL COOLING for our boosted ND. We have mounted this big Setrab unit in several locations, finding the most efficient location. Likely this becomes a kit we eventually make available for other boosted customers.

Got the win today, but not a particularly strong showing, almost neck and neck with STR times. Last event in our Supercharged NC we were 2 seconds clear of guys we trailed today in fastest WRX. Why? Tons of torque hits early, Turbo feels a bit sloppy, and not near enough tire. Car wags like a hooked bass coming off the corners on 225mm wide Hoosiers that fit in current fenders, we need flares...and we need them now. Add that I am coming off being sick, still on meds today that made me feel a little 'off' my marks, car could have done at least another second faster....looking forward to next time.

The good news is offset bushings allowed new much more aggressive alignment that felt good today, car turned-in well and I need to learn the feel of the new setup.

Is it possible to fit any of the really wide 15" 6ULs on the car, or does that require switching to way under-sized brakes? Seems like a 15x10 or 15x11 would let you run a ton of rubber under there, assuming that you can actually slow down for corners, too.

Brian wrote:Start of SCCA Autocross Season...and First Event in SSM

Got the win today, but not a particularly strong showing, almost neck and neck with STR times. Last event in our Supercharged NC we were 2 seconds clear of guys we trailed today in fastest WRX. Why? Tons of torque hits early, Turbo feels a bit sloppy, and not near enough tire. Car wags like a hooked bass coming off the corners on 225mm wide Hoosiers that fit in current fenders, we need flares...and we need them now. Add that I am coming off being sick, still on meds today that made me feel a little 'off' my marks, car could have done at least another second faster....looking forward to next time.

The good news is offset bushings allowed new much more aggressive alignment that felt good today, car turned-in well and I need to learn the feel of the new setup.

We got track days where the big brakes are sure nice to have, so likely need to go custom 17x10....unfortunately. It is that or 17x10 6UL with conversion from 4 lug to 5 lug adding a few more pounds per corner.